Numerical Estimation of Exhaust Gas Emission From Tunnel Portal With Forced Extraction System

In recent years, exhaust gas emission out of tunnel portals has been a problem. In order to maintain the environment around the tunnel portal, a concentrated exhaustion system is installed in some tunnels. In the area between the suction port and the portal, the air flows in the opposite direction to the traffic, so that the pollutant is sucked toward the exhaustion port. In order to grasp the detailed phenomena, the authors investigated quantitatively the extent of the pollutant, which is brought out of the tunnel portal, in terms of a three-dimensional numerical analysis. This simulation system includes a sliding mesh algorithm in order to express the movement of vehicles. A typical result of the suction velocity of 1.0 m/s showed that almost no emission out of the tunnel is observed in small car traffic.